QCD corrections to vector boson pair production in gluon fusion including interference effects with off-shell Higgs at the LHC

TL;DR

This paper calculates NLO QCD corrections to gluon fusion production of vector boson pairs, including interference effects with off-shell Higgs, revealing large corrections especially near the ZZ threshold, with implications for LHC measurements.

Contribution

It provides the first detailed NLO QCD correction analysis for interference effects between prompt and Higgs-mediated vector boson pair production in gluon fusion at the LHC.

Findings

QCD corrections to interference are large and comparable to signal and background corrections.

Corrections to interference vary rapidly around the ZZ production threshold.

In WW production, corrections to interference are larger than those to signal or background.

Abstract

We compute next-to-leading order (NLO) QCD corrections to the production of two massive electroweak bosons in gluon fusion. We consider both the prompt production process $gg \to VV$ and the production mediated by an exchange of an s-channel Higgs boson, $gg \to H^* \to V V$. We include final states with both on- and off-shell vector bosons with leptonic decays. The gluonic production of vector bosons is a loop-induced process, including both massless and massive quarks in the loop. For $gg \to ZZ$ production, we obtain the NLO QCD corrections to the massive loops through an expansion around the heavy top limit. This approximation is valid below the top production threshold, giving a broad range of invariant masses between the Higgs production and the top production thresholds in which our results are valid. We explore the NLO QCD effects in $gg \to ZZ$ focusing, in particular, on the interference between prompt and Higgs-mediated processes. We find that the QCD corrections to the interference are large and similar in size to the corrections to both the signal and the background processes. At the same time, we observe that corrections to the interference change rapidly with the four-lepton invariant mass in the region around the ZZ production threshold. We also study the interference effects in $gg \to WW$ production where, due to technical limitations, we only consider contributions of massless loops. We find that the QCD corrections to the interference in this case are somewhat larger than those for either the signal or the background.